If you have FormComponents in a ListView you need to call setReuseItems(true) on the ListView. Otherwise the ListItems will be recreated before rendering which results in them losing their "converted input" (what Wicket calls the submitted value).
Instead of simply calling setReuseItems(true) on the ListView, which would've solved the problem, it was instead replaced by a proper FormComponent for dealing with this exact case (a CheckboxMultipleChoice component). This reduces the amount of code required and more clearly communicates intent. The change required some minor test refactoring.
